Which time complexity is better N*(2^N) or N^2 and why?
N*(2^N) or N^2
>Solution :
N*(2^N) is exponential.
If you take n=10, for example, you get 10240
N^2 is merely polynomial.
If you take n=10, for example, you get 100
Exponential is worse than polynomial for large N, and even for reasonable Ns, in your case. To see it intuitively, imagine growing N by 1. In the polynomial case, the result grows by a fraction ((N+1) / N) ^ 2. It grows, but not much. In the exponential case, growing N by 1 doubles the result.